Port expansion system

ABSTRACT

A user configurable, modular port expansion system allows the user of a host system such as a USB-enabled personal computer to customize a desired configuration of one or more peripheral device modules without the use of cables between modules. The peripheral device modules are physically and electrically connectable to each other side-by-side between a hub end module and a power end module in any sequence so that there can be provided, within the limits of the host port specification, virtually any number of selected, expanded functions in any combination. The peripheral device modules may include, by way of example, a standard parallel DB-25 port module, a two-port serial PS/2 module, a two-port serial DB-9 module, a four- or seven-port USB hub, an RJ-11 Ethernet LAN module, and an RJ-11 modem module. Where the host port is USB compliant, power to the peripheral device modules may be supplied by the host system via a USB standard cable connected to the USB port of the hub end module, or, if more power is required, by an external a.c. power adapter connectable to the power end module. The power end module may also include an USB expansion port.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of provisional patent applicationSer. No. 60/142,733 filed Jul. 8, 1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a port expansion system forconnecting a single port, such as a USB port, on a host system such as apersonal computer (PC) to various computer peripheral devices andfunctions, and particularly to such an expansion system that is userconfigurable so as to provide a high degree of flexibility andefficiency in the connection of the host system to a wide selection ofperipheral devices and functions.

2. Description of the Prior Art

Although the invention and its background will be described chiefly inthe context of the USB standard bus interface or protocol, it will beevident to those skilled in the art that the invention may be used withother standard bus interfaces including IEEE 1394, also called“Firewire” or “i.Link”, and SCSI.

The difficulty of connecting and properly operating the many differentkinds of personal computer peripheral devices and functions such asprinters, scanners, digital cameras, modems, disk drives, and so forth,led to the adoption of the Universal Serial Bus (USB) standard whichprovides a hot pluggable, “plug and play”, cascadable serial interfaceusing a low cost standard socket for adding external peripheral devicesand functions. The Universal Serial Bus Specification Rev. 1.1 datedSep. 23, 1998 is incorporated herein by reference in its entirety.Because power as well as data are transmitted through USB cables, somelow power devices can be operated without the need for separate poweradapters. The USB specification allows up to 127 peripheral devices tobe connected to a single PC using USB hubs and defines how theseperipheral devices can be connected together so that a host can use theresources provided by each device. USB ports are already found on manynew PCs and a wide variety of USB peripherals are already on the market.Legacy-free PCs with one or perhaps two USB ports to connect peripheralsare also becoming available. Such PCs do not incorporate traditional,standard interfaces.

There are currently available numerous converters for connecting a USBport on a PC or USB hub to traditional interfaces including serialports, parallel ports, RJ-45 Ethernet LAN ports, and RJ-11 modem ports.These converters may also include one or more USB ports. However, theconverters are housed within individual enclosures requiring a separatecable to attach each enclosure to a host system or to a hub.

Also presently available are multifunction USB hubs. For example, onesuch multifunction hub expands a USB-enabled PC to provide fouradditional USB ports along with three traditional ports consisting oftwo serial ports and one parallel printer port. However, such amultifunction USB hub is integrated into a single housing so that only afixed number and combination of peripheral device or function ports ismade available.

SUMMARY OF THE INVENTION

Broadly, the present invention provides a user configurable, modularport expansion system allowing the user of a host system such as aUSB-enabled PC to customize a desired configuration of one or moreperipheral device or function modules without the use of cables betweenmodules. The peripheral device modules are physically and electricallyconnectable to each other side-by-side between first and second endmodules in any sequence so that there can be provided, within the limitsof the host system port specification, virtually any number of selected,expanded functions in any combination. The peripheral device modules mayinclude, by way of example, a standard parallel DB-25 port module, atwo-port serial PS/2 module, a two-port serial DB-9 module, a four- orseven-port USB hub, an RJ-11 Ethernet LAN module, and an RJ-11 modemmodule.

The invention further provides for the releasable or detachable couplingof the various peripheral device modules. Thus, the user can easilyconnect and separate the modules manually to readily custom design andassemble any desired combination and number of peripheral device moduleswithin the limits of the host port specification. The mechanicalcoupling between adjacent modules includes mating connectors which alsoserve to transmit the required electrical signals between the individualdevice modules of the port expansion system and between the portexpansion system and the host system thereby eliminating the need forexternal hubs and individual cables to the various modules. A techniquefor passing signals between the peripheral device modules allow theperipheral device modules to be connected together in any sequence, thusallowing a user to custom-configure a port expansion system to theuser's individual requirements. In addition, the system can bedisassembled and the peripheral device modules reassembled in adifferent order if desired. By making available a variety of individualperipheral device modules, a user can purchase and add such modules toan existing system in building block fashion to mix and matchperipherals and network connections.

More specifically, in accordance with the invention, there is provided amodular port expansion system for connecting peripheral devices to ahost system, the host system including a host port providing acommunication link for signals compliant with an industry standardprotocol. The port expansion system comprises a hub module including ahost port connectable to the host port on the host system; a downstreamconnector defining a plurality of slave ports, each slave port providinga communication link for signals compliant with the industry standardprotocol of the host port on the host system; and a hub module interfacecircuit interconnecting the host port and the plurality of slave ports.The system further includes a peripheral device module for coupling aperipheral device to the hub module, the peripheral device module beingdirectly connectable to the downstream connector on the hub module. Theperipheral device module includes a peripheral device port, connectableto the peripheral device, providing a communication link for signalscompliant with an industry standard protocol which may be the same as ordifferent from the protocol of the host port on the host system. Theperipheral module further includes an upstream connector releasablymateable with the downstream connector on the hub module, the upstreamconnector defining a plurality of ports corresponding to the slave portsdefined by the downstream connector on the hub module. The upstreamconnector on the peripheral device module and the downstream connectoron the hub module provide a direct, mechanical and electricalinterconnection between the hub and peripheral device modules. Theperipheral device module incorporates a peripheral device interfacecircuit connected between one of the ports on the upstream connector andthe peripheral device port. Last, the peripheral device module has adownstream connector for mechanically and electrically connecting theperipheral device module directly to a releasably mateable upstreamconnector on another module.

In accordance with another aspect of the present invention, theplurality of ports defined by the upstream connector on the peripheraldevice module includes a first port, a second port and successive portsand the downstream connector on the peripheral device module defines aplurality of ports including a first port and successive ports. Thefirst port on the upstream connector is connected to the interfacecircuitry of the peripheral device module. The second and successiveports defined by the upstream connector on the peripheral device moduleare sequentially connected to the first and successive ports on thedownstream connector of the peripheral device module, along the lines ofa “shift one” architecture. In this way, peripheral device modules canbe connected together in any sequence.

A port expansion system in accordance with the present invention furtherincludes a power end module connectable to the hub module, or to aperipheral device module, and which forms the end of the port expansionsystem opposite that of the hub end module. The power end moduleincludes a connector for connection to an external power supply forpowering the system in the event the system requires power above apredetermined level. The power end module may also include an expansionport for daisy chaining port expansion systems or for direct connectionto one or more peripheral devices.

In accordance with a preferred embodiment, the port expansion system ofthe present invention utilizes standard, mateable DB-25 connectors forproviding electrical and mechanical coupling between adjacent modules.Although the mechanical interconnection between adjacent modulesafforded by the mateable DB-25 connectors provides sufficient structuralintegrity, such mechanical joinder of adjacent modules is preferablysupplemented by means for releasably latching the modules together. Thecombination of the mechanical interconnection provided by the DB-25connectors and the latching means results in a structure that has therigidity and sturdiness approaching that of an integral or one pieceunit, and creates the appearance of a one piece or solid blockconstruction, yet nevertheless permits easy manual separation of themodules.

BRIEF DESCRIPTION OF THE DRAWINGS

Further benefits, advantages and features will become evident from thedetailed description of the preferred embodiments, below, when read inconjunction with the accompanying drawings in which:

FIG. 1 is a block diagram of a port expansion system in accordance withone specific, exemplary embodiment of the invention;

FIG. 2 is a rear perspective view of another embodiment of the portexpansion system of the present invention;

FIG. 3 is a front perspective view of the system shown in FIG. 2;

FIG. 4 is a rear/right side perspective view of an example of aperipheral device module in the form of a 7-port USB hub that may formpart of a port expansion system in accordance with the presentinvention;

FIG. 5 is a rear/left side perspective view of the module of FIG. 4;

FIG. 6 is a front elevation view, in cross section, showing details of alatch mechanism for coupling adjacent modules of the port expansionsystem of the present invention;

FIG. 7 is a side elevation view, partly cut away and partly in sectionof another example of a peripheral device module in the form of aUSB-to-parallel port module;

FIG. 8 is a simplified perspective view of a printed circuit boardassembly forming part of the peripheral device module of FIG. 7;

FIG. 9 is a front/right side perspective view of a power end moduleforming part of the port expansion system of the invention;

FIG. 10 is a front/left side perspective view of the power end module ofFIG. 9;

FIG. 11 is a block diagram of a port expansion system in accordance withanother specific, exemplary embodiment of the invention showing theelectrical interconnections within and between the modules thereof;

FIG. 12 is a block diagram of an example of a seven (7) port USB hub endmodule that may be used in a port expansion system in accordance withthe present invention;

FIG. 13 shows a representation of a DB-25 connector for coupling theadjacent modules of a port expansion system of the invention, along withthe connector pinouts and pin assignments thereof;

FIG. 14 is a block diagram of an example of a power end module that maybe used in a port expansion system in accordance with the presentinvention;

FIG. 14a is a table showing the sources of system bus power for variousconditions;

FIG. 15 is a block diagram showing the general form of a typicalperipheral device module adapted to be connected between the hub andpower end modules of a port expansion system in accordance with theinvention;

FIG. 16 is a block diagram of a USB-to-global modem peripheral devicemodule;

FIG. 17 is a block diagram of a USB-to-Ethernet LAN peripheral devicemodule;

FIG. 18 is a block diagram of a USB-to-parallel port peripheral devicemodule;

FIG. 19 is a block diagram of a USB-to-dual serial DB-9 port peripheraldevice module;

FIG. 20 is a block diagram of a quad port USB hub peripheral devicemodule; and

FIG. 21 is a block diagram of a USB-to-dual serial PS/2 port peripheraldevice module.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following detailed description is only illustrative of theinvention. Various alternatives and modifications can be devised bythose skilled in the art without departing from the spirit of theinvention. For example, although the invention will be describedspecifically for use with the USB standard bus interface or protocol, itwill be evident to those skilled in the art that the invention hasapplicability to other standard bus interfaces such as IEEE 1394, alsocalled “Firewire” or “i.Link”, and SCSI. Accordingly, the invention isintended to embrace all alternatives, modifications and variations asfall within the scope of the appended claims.

FIG. 1 shows in block diagram form a port expansion system 10 inaccordance with a first specific, exemplary embodiment of the invention,for attaching a variety of computer peripheral devices to a host system12 which, in the example shown, is in the form of a notebook computer.As used herein, the term “peripheral device” is used in a broad sense,encompassing any physical entity for performing a function so as toprovide a capability to the host system. Accordingly, “peripheraldevices” may include, by way of example and not limitation, printers,scanners, speakers, digital cameras, Zip® drives, business card readers,keyboards, mice, joysticks, as well as telephone lines, Ethernet localarea networks, integrated services digital network (ISDN) and digitalsubscriber line (DSL). The system 10 comprises a series of physically,that is, electrically and mechanically, interconnected modules includinga first or hub end module 14, a second or power end module 16 and fiveperipheral device modules 17-21 in between the hub and power endmodules.

The hub end module 14 includes a USB host port 22 connected by means ofa cable 24 to a USB port 26 on the host system 12. The hub end module 14is the system front-end and interfaces the USB host system 12 with theport expansion system 10 via seven (7) USB slave ports to support up tosix (6) peripheral device modules along with the power end module 16.The power end module 16 includes a USB expansion port 30 for connectingthe system 10 to one or more additional or cascaded port expansionsystems 32. Alternatively, the USB port 30 may be connected toadditional USB hubs or USB-enabled peripheral devices or functions (notshown). The power end module 16 further includes a power jack 34 forconnecting the system 10 to an external power source such as an a.c.power adapter 36 or equivalent battery pack by means of a plug 37. Suchan external power source may be required if a particular configurationof the system 10 requires more power than that available from the powerbus on the USB port 22 of the hub module 14.

In the particular example of FIG. 1, the five peripheral device modules17-21 include the following: a USB-to-dual serial DB-9 port module 17one of the DB-9 ports 38 of which is shown connected to a business cardreader 40; a USB-to-single parallel port (IEEE-1284) module 18 having aparallel output port 42 shown connected to a printer 44; aUSB-to-Ethernet module 19 having an RJ-45 port 46 connected to anEthernet LAN 48; a USB-to-telephone line/phone modem module 20 havingtwo RJ-11 ports, one of which (50) is shown connected to telephone lines52; and a USB-to-dual serial PS/2 port module 21 shown connected, by wayof example, to a mouse 54 and a keyboard 56.

FIGS. 2 and 3 are rear and front perspective views, respectively, of apractical example of an assembled port expansion system 60 in accordancewith the invention. The system of FIGS. 2 and 3 includes a first end orhub module 62, a second end or power end module 64 and six user selectedperipheral device modules 66-71 connected between the end modules. Theperipheral device modules are connected side-by-side in the followinguser selected sequence: a dual serial PS/2 port module 66; a modemmodule 67 having dual RJ-11 jacks; an Ethernet LAN module 68 having asingle RJ-45 jack; a 7-port USB expansion hub module 69; a parallel portmodule 70; and a dual serial DB-9 port module 71. The hub end module 62includes a USB port 72 for connecting the system 60 to a host systemsuch as a desktop PC or notebook computer. The power end module 64 has aUSB expansion port 74 and a jack 76 for connection to an external powersupply, as already explained. With reference to FIG. 3, the peripheraldevice modules 66-71 include front surfaces 78-83 carrying light bars84-89, respectively, fabricated of a transparent or translucent lightconducting plastic. Each of the light bars 84-89 transmits light fromone or more light sources, for example, LEDs, within the module toindicate to the user the status and/or activity of that module, as willbe further explained below. The hub end module 62 may also include astatus/activity indicator comprising a light pipe 90, visible to theuser, illuminated by an internal light source responsive to the statusand/or activity of the end module 62. The power end module 64 includes asimilar status and/or activity indicating light pipe 92.

With reference to FIGS. 4 and 5, there is shown certain of the detailsof an example of a peripheral device module in the form of a 7-port USBhub module 100. The module 100 includes a molded plastic housing 102comprising an upper housing portion 104 and a lower housing portion 106joined by screws or other attachment means (not shown). The module 100includes a rear panel 107 carrying seven USB ports 108 each comprising aUSB Type-B connector. The housing 102 further has a right side wall 110having an elongated opening 112 through which projects an upstream DB-25male connector or plug 114 for releasable connection to a mating DB-25female connector or jack carried by an adjacent module, so as to providea physical, that is, mechanical and electrical, interconnection betweenthe adjacent modules. The module 100 includes intermodule latching meanssupplementing the mechanical interconnection afforded by the matingDB-25 connectors. Specifically, projecting from the upper portion of theright side wall 110 of the module 100 is a pair of spaced apart,resilient plastic tabs 116 formed integrally with the upper portion 104of the housing and positioned to enter mating apertures in the left sidewall of an adjacent module. Each tab 116 includes at its outer extremitya barb-like enlargement 118.

Formed in the lower portion of the right side wall 110 of the module 100is a pair of spaced apart apertures 120 adapted to receive acomplementary pair of tabs projecting from the lower portion of the leftside wall of the housing of an adjacent module. As shown in FIG. 5, thehousing 102 of the module 100 includes a left side wall 122 having anelongated opening 124 through which projects a downstream DB-25 femaleconnector or jack 126 for receiving the DB-25 plug on the right side ofan adjacent module. Formed in the upper portion of the left side wall122 of the upper housing portion 104 is a pair of spaced apart apertures128 for receiving tabs projecting from the right side wall of anadjacent module. Similarly, the lower portion of the left side wall 122of the module 100 carries projecting tabs 130 each having at its outerextremity a barb-like outer enlargement 132. As used herein, the term“upstream connector” refers to a DB-25 module connector that iselectrically closest to the host system 10. Conversely, the term“downstream connector” refers to a DB-25 module connector that iselectrically farthest from the host system 10.

The module 100 includes a front wall 134 carrying a longitudinallyextending light bar 136 illuminable by an internal light sourceenergizable in response to status and/or activity signals.

FIG. 6 is a cross section view showing portions of adjacent modules 140and 142 to illustrate the manner in which the latching means in the sidewalls of adjacent modules are coupled to aid in releasably attachingtogether the modules of a port expansion system in accordance with theinvention. The module 140 includes a housing 144 having a right sidewall 146 the upper portion of which has outwardly projecting tabs, oneof which (148) is shown and which is received by an aperture 150 in theleft side wall 152 of the adjoining module 142. A barb-like enlargement154 on the outer extremity of the tab 148 engages the inner surface 156of the left side wall 152 of the module 142. A complementary tab 158 onthe left side wall 152 of the module 142 is received by an associatedaperture 160 in the right side wall 146 of the module 140.

Although use of a latching means such as that described is preferred,such means can be omitted, reliance for the integrity of the mechanicalcoupling of the modules thus being placed solely on the DB-25connectors. Still further, it will be evident that the gender of themating connectors can be reversed arid that the connectors are notlimited to DB-25 connectors; such connectors, however, are preferredbecause they are readily available, relatively inexpensive and durable.Last, it will be evident that the references to “left side” and “rightside” are for convenience only to facilitate the description of theinvention, and are not to be construed in a limiting sense.

FIGS. 7 and 8 depict another example of a peripheral device module inthe form of a USB-to-parallel port (IEEE-1284) or Centronics module 170,and show details of the interior thereof. Although a specific module isshown in FIGS. 7 and 8, it will be appreciated that the structure of theinterior of the module depicted is generally representative of thevarious modules that may form a port expansion system in accordance withthe invention.

The peripheral device module 170 of FIGS. 7 and 8 includes a moldedplastic housing 172 having an upper housing portion 174 and a lowerhousing portion 176; parallel, left and right side walls 178, 180; andparallel, longitudinally extending front and rear walls 182, 184.Mounted within the lower housing portion 176 is a printed circuit board(PCB) 186 having an upper surface 188; front and rear margins 190, 192;and left and right side margins 194, 196. Mounted on the upper surface188 of the PCB are electronic circuit components, including interfacecircuitry, represented by the block 198; a bracket 200 carrying adownstream DB-25 receptacle or jack 202 along the left side margin 194of the PCB; a second bracket 204 carrying an upstream DB-25 plug 206along the right side margin 196; and a third bracket 208 carrying aDB-25 jack 210 along the rear margin 192. The left and right side jackand plug connectors 202, 206 are connectable to mating DB-25 connectorson adjacent modules to provide mechanical and electricalinterconnections between the modules, as already explained. The rearDB-25 receptacle 210 provides a parallel port conforming to theIEEE-1284 specification connectable by means of a cable to a peripheraldevice such as a printer, all as well known in the art. The right sideor upstream DB-25 plug 206 projects through an elongated opening 212 inthe right side wall 180; a similar opening in the left side wall exposesthe downstream DB-25 receptacle or jack 202.

Mounted on the PCB 186 along the front margin 190 thereof is a lightsource 216, such as a light emitting diode (LED), energizable by thecircuitry 198 in response to predetermined module status and/or activityconditions. Such status/activity indicators are generally well known inthe art. The light source 216 is optically coupled with a light bar 218of light conducting plastic such as LEXAN (a trademark of GeneralElectric for polycarbonate compositions) carried by the front wall 182of the module 170. Illumination of the light bar 218 by the light source216 thus provides a user with an indication of the status and/oractivity of the peripheral device module. It will be evident that eachperipheral device module may contain more than onestatus/activity-indicating light source and that such plural lightsources may have different colors. Further, instead of a single lightbar 218, a plurality of lights bars may be disposed end-to-end along thefront wall 182 of the module 170, each associated with a separate lightsource. Still further, the light bar(s) may be eliminated and the lightsource(s) may be mounted along the front wall 182 of the module so as tobe directly visible to a user. Last, it will be obvious that the lightbar(s) or light source(s) may be mounted on portions of the housingother than the rear wall.

FIGS. 9 and 10 are perspective views of a typical power end module 230.The hub end module is similarly constructed. The module 230 comprises amolded plastic housing 232 including a right or inner side wall 234having an elongated opening 236. Projecting through the opening 236 is aDB-25 plug 238 adapted to be connected to a mating DB-25 receptacle orjack on an adjoining module to provide a mechanical and electricalinterconnection therewith, as already described. The right side wall 234of the module 230 further includes latching means in the form of spacedapart tabs 240 and apertures 242, also as already described. Last, themodule 230 includes a status/activity indicating light bar having anouter, visible surface 244 exposed adjacent the upper rear corner of themodule. The power end module will be further described below inconnection with FIG. 14.

FIG. 11 is a block diagram of a port expansion system 250 according tothe invention showing in simplified form the signal and powerinterconnections between the modules. The system 250 includes a hub endmodule 252 (shown in greater detail in FIG. 12), a power end module 254(shown in greater detail in FIG. 14) and three peripheral device modules256, 258 and 260 connected between the hub and power end modules. Theperipheral device modules 256, 258 and 260 are shown in generalizedform; it will be understood, however, that each of these modulestranslates USB protocol signals to the protocol of a specific peripheraldevice connected to the module. The hub end module 252 in FIG. 11includes a standard USB Type-A connector 262 for connection to a hostsystem and a 7-port hub controller 264 connected to the four terminalsof the USB connector 262. On the downstream side, the 7-port hubcontroller 264 provides USB data (D+ and D−) signals to seven slaveports, numbered as lines 1 through 7, defined by sets of contacts on adownstream DB-25 receptacle or jack 266, as well as ground lines, shownfor simplicity as a single ground line (GND) 268. The slave port 7 is apass-through to a USB expansion port 272 on the power end module 254. Asalready noted, the USB expansion port 272 on the power end module 254,which is defined by a USB Type-B connector, may be connected to aUSB-enabled peripheral device or hub or may be used to further expandthe peripheral devices and functions available to the host system bycascading or daisy-chaining additional port expansion systems.

The modules 256, 258 and 260 include interface or protocol conversioncircuits 276, 278 and.280, respectively, connected to connectors 282,284 and 286, respectively, which may be coupled to various peripheraldevices such as those shown in FIG. 1. The various modules arephysically, that is, electrically and mechanically, connected by meansof 25-pin DB-25 jacks and plugs as already explained. Thus, the DB-25jack 266 on the hub end module 252 is coupled to a DB-25 plug 288 on theperipheral device module 256; the modules 256 and 258 are coupled by aDB-25 jack 290 and plug 292; and so forth, each connector definingidentical ports 1-7.

The system 250 includes a power bus line (VCCBUS) 294 which, like theground line (GND) 268, is common to all of the modules and powers thecircuitry within each module.

It will be seen that the same basic wiring is used for the various USBperipheral device modules 256, 258, 260 with USB data line or portnumber 1 (in practice, comprising two lines D+ and D−) connected to theinterface circuits 276, 278 and 280; line or port 2 of the upstreamplugs being connected to port 1 of the downstream jacks; port 3 on theupstream plugs being connected to port 2 of the downstream jacks, and soforth. Such a “shift one” architecture permits the user to arrange up tosix USB device modules in any sequence between the hub and power endmodules. The power end module 254 includes a regulator circuit 296connected to the power bus 294 and to a power jack 298 which may becoupled to an external power supply, as shown in greater detail in FIG.14.

FIG. 12 is a more detailed block diagram of a practical embodiment of ahub end module 300 that may be used as the “front end” of a portexpansion system in accordance with the invention. The module 300, aswell as the other modules of the system, utilizes standard, commerciallyavailable electrical and electronic components whose specifications andoperation are well known in the art and therefore need not be describedin detail. The principal component of the hub end module is a 7-port USBhub controller 302 which can support up to seven downstream USB slaveports denoted in FIG. 12 as “Port-1” through “Port-7”. These ports aredefined by sets of contacts on a downstream DB-25 connector receptacleor jack 304 carried by the module 300. The hub end module 300 furtherincludes host USB port comprising a standard 4-pin USB Type-A connector306 for connecting the module by means of a standard USB cable to a USBport on a host system such as a notebook computer. As already explained,the DB-25 jack 304 is connectable to a mating upstream DB-25 plug on anyperipheral device module, or to a power end module.

The module 300 includes a power bus (VCCBUS) 308 connected to the outputterminal 310 of an overcurrent power switching circuit 312. The input314 of the circuit 312 is connected to the host power bus (HOSTVCC)terminal 316 on the connector 306. The circuit 312 has an enableterminal (EN) 318 to which is connected a control line (VCCSEL) 320. Thehub end module 300 operates in either a bus-powered mode or aself-powered, ganged port power management mode depending upon thecurrent drawn by the downstream peripheral device modules, pursuant tothe USB Specification, Rev. 1.1, Sections 7.2, et seq.

In the bus-powered mode, the power bus 308 is energized by the HOSTVCCline on the USB port via the overcurrent power switching circuit 312. Inthe bus-powered mode, the hub end module 300 is capable of supplying toeach downstream USB port 100 mA for up to four (4) low-power deviceclass functions. The overcurrent power switching circuit 312 provides abus power off function when the downstream ports draw a total currentexceeding 500 mA from the host system.

As will be further explained in connection with FIG. 14, in theself-powered mode, a +5 VDC power supply incorporated in the power endmodule provides power to the power bus (VCCBUS) 308. In this power mode,the hub end module is capable of supplying to each downstream USB port500 mA for up to seven (7) low-power or high-power device classfunctions. The /OVRCUR1-/OVRCUR6 terminals on the controller 302 (shownfor simplicity as a single terminal 322) may be tied together for gangedmode operation and be used for overcurrent condition indication andpower switch control.

As already explained, the downstream slave “Port-7” is a pass-throughUSB port connected to the USB expansion connector on the power endmodule. Power management for “Port-7” is handled separately via a powerswitching and overcurrent protection circuit 324. When the controller302 detects a downstream Port-7 fault, power is removed by the switchcircuit 324 from Port-7 only, thus allowing the peripheral devicemodules to continue normal operation.

A transient suppressor 326 is connected across the various pairs of USBport data lines to reduce in-rush current and voltage spikes. Althoughnot shown in all instances, such transient suppressors are connected tothe data line pairs of each of the remaining modules.

The hub end module 300 also includes a low-dropout voltage regulator 328connected between the power bus 308 and the VCC terminal 330 on thecontroller 302 to provide the required +3.3 VDC VCC to the controller302.

The hub end module 300 further includes an LED display 332 including alight pipe having an exterior surface visible to the user (FIG. 3) thatis illuminated by three LEDs connected to the controller and havingdifferent colors indicating the following:

Self-Power On—Green

Bus-power On—Yellow

Overcurrent—Red

FIG. 13 shows a representation of a typical DB-25 connector 336 (therepresentation shown being applicable to a front view of a DB-25 jackand to a rear view of a DB-25 plug), the connector pinouts and the pinassignments. The pin numbers are identified on the block representingthe DB-25 jack 304 in FIG. 12.

With reference to now to FIG. 14, there is shown a practical example ofa power end module 340 including an upstream DB-25 connector plug 342mateable with the DB-25 jack of any of the peripheral device modules orof the hub end module, and a USB Type-B expansion connector 344connected to “Port-7” of the DB-25 plug 342 through terminationcircuitry 346 providing compliance with FCC, UL and USB requirements. Asalready noted, the connector 344 permits cascade connection to anotherport expansion system or to one or more standard USB devices. The module340 further includes a power bus (VCCBUS) 348 (connectable to the powerbuses of the other system modules via the intermodule DB-25 connectors)and a voltage regulator 350 for supplying +5 VDC (EXTVCC) withovercurrent protection to the power bus 348 in the self-powered mode ofoperation, from an external power supply 352 via an external power jack354. A switch circuit 356 detects whether the external power supply 352is plugged in or not, and provides at an output 358 the control signalVCCSEL which is applied to the enable (EN) terminal 318 of the switch312 in the hub module 300 (FIG. 12) to switch the VCCBUS power sourcebetween HOSTVCC and EXTVCC. It will be seen that the only connections topower end module 340 via the the DB-25 plug 342 comprise power, groundand the “Port-7” pass-through connections to the USB connector 344.

The module 340 also includes an LED display 359 comprising a light pipe(such as the light pipe 92 on the power end module 64 in FIG. 3)illuminable by two LEDs to provide the user with the followingindications:

Green—USB port 344 ready

Red—USB port 344 overcurrent

FIG. 14a is a table showing the source of power on the power bus(VCCBUS) for various operating conditions. Thus, with both the hub andpower end modules connected in the system (“in”), but with the externalpower supply 352 unplugged (“out”), the control signal VCCSEL applied tothe enable terminal 318 of the electronic switch 312 in the hub endmodule 300 will be high thereby applying HOSTVCC to the power bus(bus-powered mode). Conversely, in the self-powered mode,with the powersupply 352 plugged into the jack 354, VCCSEL goes low, disconnectingHOSTVCC so that the power bus will be powered by EXTVCC appearing at theoutput of the voltage regulator 350.

FIG. 15 is a block diagram depicting the general form of a peripheraldevice module 360, and includes a DB-25 plug 362 on the upstream side ofthe module and a DB-25 jack or receptacle 364 on the downstream side.The pin assignments for the connectors 362 and 364 are as shown in FIG.13. The module 360 includes pass-through power bus (VCCBUS), VCCSELcontrol signal, and ground lines 366, 368 and 370, respectively. Themodule 360 includes an interface circuit, for example, a controller 372providing conversion of the USB data signals appearing on “Port-1” ofthe DB-25 plug 362 to the protocol of the peripheral device adapted tobe connected to the device or function connectors 374 supported by themodule. The typical module 360 includes an LED display 376 responsive tostatus and/or activity signals generated by the interface circuit 372.

In accordance with the “shift one” architecture permitting theperipheral device modules to be connected in any sequence between theend modules, within the peripheral device module 360, “Port-1” (USB datalines D1+ and D1− assigned to pins 3 and 16) on the upstream DB-25connector or plug 362 is connected to the USB peripheral deviceinterface circuit 372, “Port-2” (USB data lines D2+ and D2− on pins 17and 5) on the plug 362 is connected to “Port-1” (contacts 3, 16) of theDB-25 jack 364 on the downstream side, “Port-3” (USB data lines D3+ andD3− on pins 6, 19) on the plug 362 is connected to “Port-2” (contacts17, 5) of the DB-25 jack 364, and so forth. There is no connectioninternally within the peripheral device module 360 to “Port-6” (contacts23, 11) on the DB-25 jack 364.

Several specific examples of peripheral device modules will now bebriefly described with reference to FIGS. 16 to 21. Again, each of thesemodules utilizes well known components and therefore need not bedescribed in detail; in each case, the wiring between upstream anddownstream DB-25 connectors within the module is as illustrated in FIG.15, with pin assignments as shown in FIG. 13. With reference to theblock diagram of FIG. 16, there is shown a 56K global modem module 380including an upstream DB-25 connector plug 382 and a downstream DB-25connector receptacle or jack 384, both with pin assignments as set forthin FIG. 13. The module 380 further comprises a USB controller 386, amodem chipset 388, and a data access arrangement (DAA) 390 in the formof an isolating optocoupler for global-approved modem operation.Connected to the DAA 390 is a pair of RJ-11 jacks 392 and 394 forconnection to a telephone line and a phone. The module also includes astatus/activity LED display 396.

FIG. 17 is a block diagram of a USB-to-10 Mbps Ethernet LAN module 400including upstream and downstream DB-25 connectors 402 and 404,respectively, and incorporating a single standard modular RJ-45 jack 406for connecting the module 400 to an Ethernet LAN. The module 400 furtherincludes interface circuitry comprising a USB-to-Ethernet media accesscontroller (MAC) 408, network physical layer devices 410 and 412, and anLED status/activity display 414.

With reference to FIG. 18, there is shown a USB-to-single parallel port(IEEE-1284) module 420 including an interface circuit comprising aUSB-to-IEEE-1284 bridge device 422. The bridge device 422 is connectedto an IEEE-1284 termination network 424 in turn coupled to a DB-25parallel port connector 426 adapted to be connected to a peripheraldevice such as a printer. The module 420 includes an LED display 428 forindicating to the user the power status of the module.

With reference to FIG. 19, there is shown a USB-to-dual serial DB-9 portperipheral device module 440 incorporating a USB controller 442, a dualuniversal asynchronous receiver/transmitter (UART) IC 444 and RS-232transceivers 446 and 448 coupled to DB-9 connectors 450 and 452,respectively. An LED display 454 indicates the status of the DB-9 ports.

With reference to FIG. 20, there is shown a 4-port USB hub module 460incorporating a 4-port USB hub controller 462, a quad USB power controlswitch device 464, and four USB Type A connectors 466-469. The powercontrol switch device 464 is capable of supplying 500 mA to eachdownstream USB port and can provide current limiting on a per portbasis. A 7-port USB hub module is similar to the module 460, except thatit includes a 7-port USB hub controller and two quad USB power controlswitch devices 464.

With reference to FIG. 21, there is shown a USB-to-dual serial PS/2 portmodule 480 including an interface circuit in the form of a USB-to-dualserial PS/2 port bridge device 482 and dual PS/2 termination networks484 and 486 connected to PS/2 port connectors 488 and 490, respectively.Either PS/2 port can accept a mouse or a keyboard. The module 480 alsoincludes a port status-indicating LED display 492.

We claim:
 1. A modular port expansion system for connecting a peripheraldevice to a host system, the host system including a host port providinga communication link for signals compliant with an industry standardprotocol, the port expansion system comprising: a hub module including:a host port connectable to the host port on the host system; adownstream connector defining a plurality of slave ports, each slaveport providing a communication link for signals compliant with theindustry standard protocol of the host port on the host system; and ahub module interface circuit interconnecting the host port and theplurality of slave ports; and a peripheral device module for coupling aperipheral device to the hub module, the peripheral device module beingdirectly connectable to the downstream connector on the hub module andincluding: a peripheral device port providing a communication link forsignals compliant with an industry standard protocol, the peripheraldevice port being connectable to the peripheral device; an upstreamconnector releasably mateable with the downstream connector on the hubmodule, the upstream connector defining a plurality of portscorresponding to the slave ports defined by the downstream connector onthe hub module, the upstream connector on the peripheral device moduleand the downstream connector on the hub module providing a mechanicaland electrical interconnection between the hub and peripheral devicemodules; a peripheral device interface circuit connected between one ofthe ports on the upstream connector and the peripheral device port; anda downstream connector for mechanically and electrically connecting theperipheral device module to a releasably mateable connector on anothermodule.
 2. A system, as defined in claim 1, in which: the plurality ofports defined by the upstream connector on the peripheral device moduleincludes a first port, a second port and successive ports, the firstport of the upstream connector being connected to the peripheral deviceinterface circuit; and the downstream connector on the peripheral devicemodule defines a plurality of ports including a first port andsuccessive ports and wherein the second and successive ports defined bythe upstream connector on the peripheral device module are sequentiallyconnected to the first and successive ports on the downstream connectorof the peripheral device module.
 3. A system, as defined in claim 2, inwhich: the downstream connector on the hub module defines seven slaveports supporting up to six peripheral device modules.
 4. A system, asdefined in claim 1, in which: the industry standard protocol of the hostsystem port is the same as the industry standard protocol of theperipheral device port.
 5. A system, as,defined in claim 4, in which:the industry standard protocol is compliant with the Universal SerialBus specification.
 6. A system, as defined in claim 1, in which: theindustry standard protocol of the host system port is different form theindustry standard protocol of the peripheral device port.
 7. A system,as defined in claim 6, in which: the industry standard protocol of theperipheral device port is selected from the group consisting of thefollowing protocols: standard serial; standard parallel, Ethernet LAN,modem, ISDN, DSL, and PNA.
 8. A system, as defined in claim 1, in which:the downstream connector on the hub module and the upstream connector onthe peripheral device module are DB-25 connectors.
 9. A system, asdefined in claim 8, in which: the downstream connectors on the hub andthe peripheral device modules are of one gender and the upstreamconnector on the peripheral device module is of the opposite gender. 10.A system, as defined in claim 1, in which: the hub module has a frontand a side, the host port of the hub module being disposed along saidfront of the hub module, and the downstream connector of the hub modulebeing disposed along the side thereof; and the peripheral device modulehas a front and opposite, parallel, upstream and downstream sides, andwherein the peripheral device port is disposed along the front of theperipheral device module and the upstream and downstream connectors ofthe peripheral device module are disposed along the upstream anddownstream sides, respectively, whereby the modules are directlyconnectable together in a side-by-side relationship.
 11. A system, asdefined in claim 10, in which: the side of the hub module and theupstream side of the peripheral device module include mateable,latchable tabs and apertures providing releasable, mechanical joinder ofthe modules.
 12. A system, as defined in claim 1, which furtherincludes: a power module having a side including an upstream connectormateable with the downstream connector on the hub module or on theperipheral device module; and in which: the hub module, peripheraldevice module and power module include electrical power buses, saidpower buses being connectable through the upstream and downstreamconnectors on the modules; and the power module including an externalpower supply connector, and electrical circuitry including a switch forcoupling the external power supply connector to the power bus of thepower module.
 13. A system, as defined in claim 12, in which: the powermodule includes an expansion port connected to a set of contacts on theupstream connector of the power module.
 14. A system, as defined inclaim 1, in which: the peripheral device module includes an indicatorvisible to a user responsive to status and/or activity signals generatedby the interface circuitry of the peripheral device module.
 15. Asystem, as defined in claim 14, in which: the status and/or activityindicator includes a light source energizable in response to said statusand/or activity signals, and a light conducting element opticallycoupled to the light source and visible to the user.
 16. A system, asdefined in claim 12, in which: the hub and power modules each includesan indicator visible to a user responsive to status and/or activitysignals generated by the circuitry of the module.
 17. A system, asdefined in claim 16, in which: the status and/or activity indicator ofeach of the hub and power modules includes a light source energizable inresponse to said status and/or activity signals, and a light conductingelement optically coupled to the light source and visible to the user.18. A module for connecting a computer peripheral device to a port on ahost computer system, the port providing a communication link forsignals compliant with an industry standard protocol, the modulecomprising: a housing having a front wall and opposite, parallel sidewalls; a peripheral device port, connectable to the computer peripheraldevice, disposed along the front wall of the housing, the peripheraldevice port providing a communication link for signals compliant with anindustry standard protocol; a first connector disposed along one of theside walls of the housing, the first connector having contacts defininga plurality of ports including a first port, a second port andsuccessive ports; a second connector disposed along the other side wallof the housing, the second connector having contacts defining aplurality of ports including a first port and successive ports; aninterface circuit, connected between the first port on the firstconnector and the peripheral device port; and wherein the second andsuccessive ports on the first connector are sequentially connected tothe first and successive ports on the second connector.
 19. A module, asdefined in claim 18, in which: the first and second connectors compriseDB-25 connectors of opposite gender.
 20. A module, as defined in claim19, in which: the first and second connectors each define seven ports,the second through sixth ports of the first connector being connected,respectively, to the first through the fifth ports of the secondconnector, and the seventh port on the first connector being connectedto the seventh port on the second connector.
 21. A module, as defined inclaim 18, in which: the peripheral device port is selected from thegroup consisting of the following industry standard ports: USB, serial,parallel, Ethernet LAN, modem, ISDN, DSL, and PNA.
 22. A module, asdefined in claim 18, in which: each of the side walls of the housingincludes latch means for mechanically joining the module to an adjacentmodule.
 23. A module, as defined in claim 18, which includes: anindicator visible to a user, the indicator being responsive to statusand/or activity signals generated by the interface circuit of themodule.
 24. A module, as defined in claim 23, in which: the statusand/or activity indicator includes a light source energizable inresponse to said status and/or activity signals, and a light conductingelement optically coupled to the light source and visible to the user.